Someone who spends a disturbingly long amount of time editing the site www.wikipedia.com, usually to protect pages they are interested in from vandalism and to keep them up to date.

This is usually done at the expense of other social activates like asking girls out, or talking to friends. And the seasoned wikipedian can often be seen fapping furiously after writing an article he considers to be particularly accurate.

Jenny: What do you do in your spare time?
Kearney: I'm a wikipedian, I recently corrected some glaring inaccuracies on the Captain Picard page!
Jenny: …okaaay *turns around*

Someone who gives up their free time to help build an enormously useful internet project called Wikipedia that provides loads and loads free information about any topic you could think of, accessible to everyone who has internet access. Wikipedians are often critised for not having a life by trolls who copy their work when they're supposed to write about something.

<troll>: what did u do yesterday at 6 oclock?
<wikipedian>: I finished my work on the article x on Wikipedia
<troll>: omg omg ur a faggot i played pc games wif my friends coz im cool get a life <goes to Wikipedia and copies an article so that he wouldn't have to write an essay>

The most highly-evolved form of pseudo-intellectual, correcting typos and writing about anime from their lofty ivory towers. Despite their claims to the contrary Wikipedians are an elitist cabal of pompous undergraduates, anime nuts and anal-retentives who derive meaning in their otherwise dull lives from incessantly editing and updating Wikipedia. All of the above can be confirmed by reading their biographical "user pages," where they display pedantic lists of their various heart-sinkingly inane interests in the same way a psychotic nutcase living in an attic would display shrunken heads.

Any changes to an article with which the Wikipedians disagree will throw them into confusion and panic, and it will be debated endlessly by them in their attempts to dissect and scrutinize every minutiae of human existence, no matter how worthless or trivial. This further strengthens their delusion that Wikipedia is an actual encyclopedia with any educational worth rather than a glorified video-gaming rumour mill.

A Wikipedian is the kind of person who sees a typo in an unthinkably obscure Wikipedia article at 3 in the morning, corrects it and feels really proud of himself. Console yourself with the fact that at least you're not like them.

Unless you are one of them, in which case you should probably get back to Wikipedia to write an article listing anime characters with "z" in their names or whatever the hell it is you people like to do.